Degradation of Veterinary Antibiotics by Ozone in Swine Wastewater Pretreated with Sequencing Batch Reactor

Abstract

This study assessed the potential of ozone for the degradation of nine commonly used veterinary antibiotics (five sulfonamides, three tetracyclines, and one macrolide) in swine wastewater pretreated by sequencing batch reactor (SBR). The apparent second-order rate constants for the reactions of selected antibiotics toward ozone in Milli-Q water (kO3 at pH 7.0 and T=20°C) were determined by competition kinetics as follows: sulfonamides [(1.9–6.2)×106 M-1s-1], tetracyclines (6.9×106 to 1.7×107 M-1s-1), and tiamulin (3.8×105 M-1s-1). The antibiotics could be quickly degraded by ozone in the SBR effluent with degradation rates following the order of their kO3 values. In the SBR effluent, the dissolved organic materials strongly competed for oxidants against antibiotics, while the suspended solids had insignificant influence on antibiotics degradation. The reaction mechanism was primarily direct oxidation via ozone rather than indirect oxidation via hydroxyl radicals. Overall, ozonation is a feasible polishing process, subsequent to biological treatment, for removal of residual antibiotics from swine wastewater.